A typical transmission uses a combination of selectively engageable clutches and brakes to achieve a plurality of forward and reverse gear ratios. Typically an electronically controlled hydraulic control circuit or system is employed to control solenoids and valve assemblies. The solenoids and the valve assemblies are configured to selectively communicate a pressurized hydraulic fluid to actuate the clutches and brakes.
While conventional hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. In addition, it is desirable to have hydraulic control systems that have multiple default modes that allow at least limited operability of the transmission in the event of electrical or other failures of the control system. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a transmission that includes operable default modes.